Flexible pipe, also known as flexible tube, has a variety of shapes and sizes. Flexible pipes are widely used for piping, joint, and as a protecting tube. Of these flexible pipes, particularly, there is a flexible pipe having a stand structure (hereinafter, referred to as standing flexible pipe). The standing flexible pipe is configured so that the user is able to bend freely same as a normal flexible pipe, and in addition, has capabilities of retaining the shape thereof. Such standing flexible pipe is widely employed for desk light, stand microphone, or the like. For instance, the standing flexible pipe is used as a support for a lamp, standing from the main body of the desk light, and the wiring is internally provided from the main body of the desk light to the lamp. The user is able to bend the support (the standing flexible pipe) to change the position of the lamp to a desired one.
FIG. 1 is a view of a conventional standing flexible pipe that is partially cut out for exhibiting an internal configuration. A conventional standing flexible pipe 100 includes a base wire 101 having a circular cross-section wound in a spiral manner and a subsidiary wire 102 having a substantially triangular cross-section. The subsidiary wire 102 is also wound in a spiral manner to cover the base wire 101, and is attached firmly to be fit into an external valley of the base wire 101. When the standing flexible pipe 100 is bent, friction occurs between the base wire 101 and the subsidiary wire 102 that are in contact with each other. The standing flexible pipe 100 bent retains the state (shape) with the afore-mentioned friction.
The standing flexible pipe 100 shown in FIG. 1, however, has a disadvantage in that the bearing force is weakened if the torsional force is applied to wind back more than a given amount. If the standing flexible pipe loses the retention thereof, the advantage is degraded, thus causing the problem in that, for example, the lamp of the desk light cannot be fixed at a desired position. If the user repeats twisting along the axis without understanding the structural characteristics, the afore-mentioned problem will be exposed at an early stage.
The standing flexible pipe 100 retains a bent state, with the friction between the base wire 101 and the subsidiary wire 102. However, once the torsional force is applied to wind back, the base wire 101 and the subsidiary wire 102 are not adhered to each other. For this reason, the frictional force cannot be obtained sufficiently, thereby causing degraded retention. Also, it is known that the adhesiveness between the base wire 101 and the subsidiary wire 102 gradually degrades with age.
To address the above-described problem, techniques have been proposed in Japanese Patent Application Publication No. 7-305789 and Japanese Patent Application Publication No. 7-305790. However, these techniques cannot be applied to the standing flexible pipe having a structure in which the wires are wound in a spiral manner. In other words, there is no technique for improving the bearing force of the standing flexible pipe against the torsional force to wind back.